Material depiling and handling apparatus



Feb. 26, 1963 G. E. GoLLwrrzER rs1-Al. 3,079,011

MATERIAL DEPILING AND HANDLING APPARATUS 5 Sheets-Sheet 1 Filed Oct. 6, 1960 UE Nwwd w .AQ \w\ WQNW Q Hrm): N5 8\ s. d l Nvt Il r|| MCM* I -|II1II MW A \nw\ .man l o|0|o \\Im|\l.l c

Feb. 26, 1963 G. E. GoLLwlTzl-:R ETAL 3,079,011

MATERIAL DEPILING AND HANDLING APPARATUS 5 Sheets-Sheet 2 Filed Oct. 6, 1960 Feb. 26, 1963 G. E. GOLLWITZER FAI.

MATERIAL DEPILING AND HANDLING APPARATUS Filed Oct. 6, 1960 INVENTO .SY Z' 77 z 7? S 5 f 2,7%@ f Feb 26, 1963 G. E. GoLLwn'zER ErAL MATERIAL DEPILING AND HANDLING APPARATUS 5 Sheets-Sheet 4 Filed Oct. 6, 1960 Feb. 26, 1963 G. E. GoLLwlTzER ETAL 3,079,011

MATERIAL DEPILING AND HANDLING APPARATUS Filed oct. e, 1960 5 sheets-sheet 5 5/ A ,4x54 5/ 4.4/ d? /MJ {MJ 1.1 U/y/ FQ /f g MJ w wwf E- f`1 I F551 *U swf si l j?! l /V l 5w! I 77,235 V45 I xm: f .Af/f! fi I Y L fl w 671/4 7.5'

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Patented Fein. 25, 1963 3,i37,d11 MATEREAL HEEPLNG AND HANDLING AFPARATUS George E. Gollwitzer, Mount Vernon, and Floyd F.

Forma and Herbert Bierwirth, Pittsburgh, Pa., as-

signors to Kelsey-Hayes Company, Detroit, Mich., a

corporation of Eclair/are Filed Get. 6, 1969, Ser. No. 69,935 6 Claims. (Cl. 214-1) This invention relates to a material handling apparatus and particularly to a mechanism for successively and individually removing pieces of material from a stack and depositing the pieces in a selected position adjacent the stack.

-lt is an object of the present invention to provide a material handling apparatus of the above character which is particularly suited for the handling of large, somewhat elongated pieces of. sheet material, as, for example, sheet steel.

It is another object of the present invention to provide a work handling apparatus of the above character which is relatively simple and inexpensive in construction, yet which is ruggedly built and highly reliable in operation.

it is still another object of the present invention to provide a work handling apparatus of the above character which avoids the necessity for utilizing overhead cranes or other ceiling suspended apparatus but which is relatively compact in size, is entirely iloor supported and presents a minimum obstruction to the movement of worlcmen and use of adjacent lloor space.

It is a still further object of the present invention to provide a work handling apparatus of the above character which is operable to transfer the sheets with a minimum usage of power yet which is eifective to cleanly lift the sheets off of the pile, move the sheet over a given new location and accurately deposit the sheet into position in the new location.

lt is still another object of the present invention to provide a work handling apparatus of the above character utilizing a tiltable rocker frame and vacuum operated suction cups for lifting the sheets having improved means providing a vacuum chamber adapted to be placed in communication with the suction cups.

It is still another object of the present invention to provide a work handling device of the above character which is operable to successively raise the uppermost sheet from the pile and move it to a selected location, yet will automatically return to piel; up a sheet in the event that a sheet is accidentally dropped and which will delay its operation if the sheet receiving location is not in a condition ready to receive a new shee It is a still further object of the present invention to provide a worl: handling mechanism which is particularly suited for the depiling of sheet steel and the individual handling of sheets through a roller coater mechanism preparatory to the working of the sheets in a die press.

These and other objects of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings wherein:

FiGURE l is a front elevational View with parts broken away of a worl: handling apparatus embodying the principles ofthe present invention;

FIG. 2 is a plan view of the structure shown in FIG. 1;

FIG. 3 is an enlarged sectional view of the structure illustrated in FIG. 2 taken along the line 3-3 thereof;

FIG. 4 is an enlarged rear elevational View of a portion of the structure shown in FIG. 1;

FIG. 5 is an enlarged sectional view of the structure shown in FIG. 2 taken along the line 5 5 thereof;

FIG. 6 is a sectional view of the structure shown in FlG. 5 taken along the line 6-5 thereof;

FIG. 7 is a sectional View of the structure shown in FIG. 3 taken along the line '7-7 thereof;

FIGS. 8 and 9 are wiring diagrams of a suitable control mechanism usable with the apparatus shown in FIGS. 1-7; and

PEG. l0 is a diagrammatic view of the pneumatic power apparatus utilized with the structure shown in FIGS. 1-7.

Referring now to the drawings and particularly to FIG. 3, there will be seen a conveyor, generally indicated by the numeral 12, on which the stacks or piles of sheets are loaded and conveyed to a position adjacent to a transfer mechanism, generally indicated by the numeral 14. The mechanism 14 serves to individually and successively remove the uppermost sheet from the stack in sm'd position and deposit it on a roller conveyor, generally indicated by the numeral 16. From the position in which they are deposited on the conveyor 16, the individual sheets are slidably moved therealong by a pusher mechanism, genreally indicated by the numeral 18, to a first work performing station, as, for example, the roller coater mechanism, indicated by the numeral 2h. From the roller coater mechanism Ztl the sheets are delivered to a roller conveyor 22 from which location they may be removed by any suitable means, as for example, manually. While the exact construction of the several conveyors utilized with the transfer mechanism 14 is such as to permit the convenient arrangement of suitable limit switches, as will be hereinafter described, the conveyors per se and the work performing station 2li may be varied widely within the scope of the present invention. They are described herein for the principal purpose of illustrating a complete sequence of operations for the transfer mechanism 14 in which the transfer mechanism 14 is so controlled as to delay operation until a pile has been brought into its proper deplling position and the conveyors 16 and 212 are ready to receive a new sheet. While the transfer mechanism 1d and the conveyor 16 may be utilized to feed sheets to a variety of work performing stations, the roller coater 2@ is particularly intended to provide sheet steel with a suitable coating preparatory to the working of the sheets in a die press (not shown) and the sheets may be manually or otherwise fed from the conveyor 22 directly into the press. It will be appreciated, however, that the sheets could be delivered directly from the conveyor 16 to a variety of machines for forming, coating, treating or other working of the material.

As shown in the drawings, the conveyor 12 includes a stand 24 on which are mounted two spaced rows of rollers 26 yand 28 which provi e a horizontal supporting structure for endless conveyor belts 30 and 32;, respectively. The belts are driven by a motor 34, for the purpose of advancing stacks of sheets from a loading position thereon to a position in juxtaposition to the transfer mechanism 14. A limit switch LSS is located between the belts 3i) and 32 and is intended to have its 4actuating -arm contacted by the lowermost sheet of the pile when a pile has been brought to the desired depiling position.

The conveyor 16 is arranged in parallel and closely spaced relation to the conveyor 12. The conveyor 16 includes a framework 36 which supports a pair of spaced rows of aligned rollers 3S and 4@ on which the sheets are adapted to Idirectly rest when delivered thereto by the transfer mechanism 14. A limit switch L53 is positioned between the rows of rollers 38 and 40 in a position to have its actuating arm biased when a sheet is lowered onto the conveyor 16 by the transfer mechanism 14. In addition, a second limit switch L82 is positioned between the rollers 38 and 4t? adjacent the roller coater Ztl and is provided with an actuating arm arranged to be biased by a sheet which is being fed into the roller coater but which has 'not cleared the conveyor 16. A slide-member d2 is supported beneath and between the rollers 38 and 4i) on -a pair of ways 44 for. reciprocation lengthwise of the conveyor 16.` The member 42.is provided with a pair of opstanding lugs ld6 VanddS upon whicha pair of dogs Si? and SlateV mounted,vrespectively.L The `dog 59 is provided witha forwardly facing-abutment shoulder Stpand a rearwardly vand downwardly inclined cam surface 56,'while th'edog 52'is provided with a forwardly facing abutment shoulder 58v and a rearwardly and downwardly inclined camsurface 60.Y Each of the dogs Si) and 52 is provided with ,arearward extension62 and 6d,V respectively, which seats onthe upper surface of the slide-42'and not only provides suicientweighttomaintain the dogs in the position shown,'bu`t prevents clockwise rotational movement of'thefdogs from the position inwhich they are illustrated. The slide 42is connected at its`forward end to the piston rod 66 of an air cylinder 68, which is adapted to'supply power to reciprocate the slide 42'on`its ways 44. One or the other of the dogs` 0 and 52 will'engage an end of a sheet lowered konto theconveyor 16 for the 'purpose'of moving it onto'theroller conveyor 20, as will be more fullytexplained below. c A

The transfer. mechanism 14 includes a rocker frame or transfer aIm70wh`ich is lpivotally supported on la base fra'meTI.. Allofy'the frame members of the rocker frame mare of hollow` tubular shape andere interiorly interconnectedto provide a relatively largevol'ume vacuum chambe'riwhich isconnected to a vacuum pump V7d through aY flexible conduitjditted to a lower tubular rframe member v78.* Thelower frame member 18.is provided with stub shafts 80 and82 atits opposite ends which yare journaled in pillow bloclts- 84` and 86 supported on the base 72. The'rocker frame 7 0` addition-ally includes ya' paix-fof, parallel spaced bent frame members 88A iand 90 which arepinterconnected and bracedrby a central tubular cross'frame member 92 and an upper end crossv frame member 94. Each of the-bentVfra-metrnembers S8 and 96' includes a lower straight section 96,` acentral elbow section'tv98 and an upper straightY section 100 disposed at an acute angle to the lower section 96. As may be best seenin FIG.v 3, the pivot axisof the rocker frame, which.

is-'Vdeiined bythe stubv shafts 80yand 82, is disposed below vand generally midway between the centers of the conveyors 12 and 16 with the lower frame sections 96 spanning'the' Width of the conveyor 1 6 beneath Vthe same and the upper frame sections 100 being disposed above the conveyors and extending across the width of the conveyor 16 to a position disposed labove the center ofthe conveyor 12 when the rocker frame is in the position shown in solid lines infPtG.. 3. Y

.Movement of the rocker frame 70 iseife'cted' by means of jan air cylinderv 102' which is pivotally connected at its' lower end to a floor bracket 104 `and isY provided with a' piston rod 106 carrying a clevisv 198 at its Vouter end which is pivotally joined to a brace .110 fastened between the frame lmembers SS and S90. A hydrauliccylinder 112 is disposed adjacent to the cylinder 1&2Y and is similarly pivot-ally connected to a door bracketflld` andfis provided with a piston rod`116 Ycarrying a clevis 11S'which isalso pivotally connected with thebrace 11th` Communication between the opposite-endsof the cylinder 112 is provided through agcheck valve-1201er the -recirculationV` ofv the hydraulic uid from one end ofthe cylinder 112 through thecheck'valve 120 tothe opposite end ofthe cylinden The check valve meters the-flow Iof'iiuidand provides a sinoothand uniform rate of operation for the `airrcyl'inder.

102 which,v if'uncontrolled; might otherwiseoperate in ay somewhat'jerky or excessively rapid manner.

Pivotally hung from the vrocker frarnecross member Qd adjacent the opposite'vendjthereof"are a pair of aircylinders 122aud 124. The 'cylinders`122-and'124 are provided with piston rods 126 and 12S, respectively, carrying' clevises 13b and 132 which are pivotally joined to the opposite ends of Aa channel member 134. A pair of suction cups 136 and 13S are fastened to the underside of the channel member 134 beneath the clevises 13d and 132. Each of the suction cups is provided with a downwardly presenting suction area which communicates with an extensible flexible conduit 149 and 142 which in turn are connected to a valve 144 mounted on the cross frame member 9d and communicating with the vacuum chamber formed within the rocker frame. The valve 14d thus controls the communication of the vacuum chamber with the vacuum cups 136 Vand 138 for the purpose of lifting and releasing the sheetsk of material.

Securely fastened to the cross frame member 94 adjacent the air cylinders 122 and 124 on the rear side thereof are a pair of angle iron members 146 and 148, each of which 'is providedwith a pair of integrally joined nuts 15G, each one of which serves to support the threaded shank 152 of an adjustable locating pad or abutment 154 having a rubber face 155.` A locking nut 158 may be threaded onto each shank 152 and ydrawn tight against the nut 158 for locating the rubber face 156 in any desired position.

The rubber faces 156 of the abutment members 154 are adapted to bear against the air cylinders 122; and 124 for the'purpose of limiting rearward swinging pivotal movement there'of'when the rocker frame is moved to its retracted'position, as inclicated'in broken lines in EEG. 3. Thus, whenV the rocker frame is moved to its retracted position with the airV cylinders suspended over the conveyor 16, the air cylinders 122 and 12d will be held in a perfectiy vertical position by the abutment members 154 and theworkpiece carried thereby will be prevented from swingingbeyond its intended position as a result of the mornentum'of the parts hung from the cross frame memberA 9i. Fixed to the cross frame member 94 adjacent the cylinders 122 and 124 on the forward sides thereof area pair lof angle iron members 160 and 162, also carrying abutmentv lmembers 154,1Which limit the forward swinging movement of the suction cups upon the movenient of'nthe-r`ocker frame to its forward position and assure that the air cylinders will be maintained in a vertical position when the rocker frame is brought to rest in its forward position.

Sljiewetswof material'which have been deposited on the conveyorlo are fed into the roller coater 2G, and has been previouslypdescribed. The roller coater 29 includes a pair of iirst vertically spaced rollers 164 and a second pair of verticallyV spaced rollers 166, both pairs being rotatably'interconnected by spur gears 16S and both pairs of'vrollers being driven in rotation by a motor 176 and drive chainl'iZ. The rollers 164 and 166 are covered with a .suitable coating material which will be applied to the sheets passed therebetween. When a sheet is fed between the first pair of rollers 164 it will not only be coated with thelr material covering the surface of said rollers but, as a result of the engagement of the rollers on the opposite sides thereof, the sheet will be fed through the second pair of rollers 166 and thence'onto the nal roller conveyor 22. In this position, a sheet of material will depress the actuating arm of a limit switch LS1 which is positioned between two spaced rows of rollers 174 and 176 on which the work sheets rest for sliding movement along the conveyor. In FIG. 2, the conveyor 22 is illustrated as having a second position, at which location a sheet resting on the conveyor 22 wiil depress the actuating arm of a limitV switch LSS. As will be hereinafter explained, the' limit switch L55 permits'additional control of the depiling apparatus in response to the consumption of theA sheets being depiled and assures that the sheets will not be -depiled at any greater rate than they are needed;

The operation of the mechanism of the present invention will be best understood by reference to FIGS. 8, 9

and 10. in P16158, a suitable electrical control circuit is illustrated in which conductors 173 and 1S@ are connected to the opposite side of a source of alternating electrical potential (not shown) upon the closure of a line switch Si. In describing the operation of the mechanism of the present invention, it will be first assumed that the rocker frame 70 is in a retracted position with its cups T135 and 138 raised and that the conveyors 16 and 22 are empty of sheets. In order to begin the transfer cycle, the machine operator first closes manual Switches SW1, SW2, SW3 and 8W4. It Will be noted that when the rocker frame is in its retracted position, it will engage the actuating arm of limit switch L86 and its contacts LSoa and L86!) will therefore be held open. Thus, no current will ilow through switch SW1. However, the closure of switch SW2 is effective to energize relay R2 through either normally closed contacts R31) or normally closed limit switch L89, thus causing closure of its contacts R2b and R211. The closure of switch SW3 and contacts R215 establishes an energizing circuit for motor starter relay M2 through normally closed contacts RSC and Rflb, provided that a pair of sheets is not in a position on the belt conveyor 12 opposite the transfer mechanisin 16. The energization of relay M2 causes closure of its contacts Ma, Mb and MZc (FIG. 9) to deliver current to the belt conveyor motor 34 and thus drive the belts 36 and 32. By this means, a pile which has been placed onto the conveyor 16 will be moved therealong until it contacts the actuating7 arm of L88. When this occurs, the contacts of limit switch L88 will be closed to energize relay R4 and open normally closed contacts Rib. This interrupts the energizing circuit for relay M2 and deenergizes the motor 34, to cause the belts Sil and 32 to stop with the pile of workpieces in a proper position for unloading by the transfer mechanism i6.

Simultaneously with the movement of a pile into unloading position, the rocher frame 7l) is moved from its etracted position to the forward position shown in solid lines in FIG. 3. This movement results from the energization ofthe coil of solenoid 3 by the closure of contacts la. Solenoid 3 is operatively connected to a valve 182 so as to deliver compressed air from a source of compressed air 183 to the cylinder i432 so as to move the piston rod 106 thereof in an upward direction. As the rocker frame 7 G moves forwardly, it disengages from limit switch L86 and ultimately contacts the actuating arm of limit switch L87 when it has reached its forward position, thereby closing the contacts of L87. The contacts LSda, which now close, complete a circuit through switch SW1 and the contacts of limit switch L85 to energize motor starter relay Ml. The energization of relay Ml causes closure of its contacts Mia, Mib and Mic (FIG, 9) to deliver three-phase current to the roller coater motor I7@ to drive the rollers lid-t and 166.

After the pile on the conveyor l2 has reached its proper position and the contacts of limit switch L88 have been closed, relay Rd will be energized to close its contacts R451 and complete a circuit through solenoid i. Solenoid is operatively connected to a valve 134 and when energized moves the spool of valve 184 in a direction admitting compressed air from the compressed air source 183 to the cylinders 122 and 124 in a direction electing the descent of piston rods lZd and 12S. When the suction cups malte contact with the top sheet on the pile, limit switch L84 will be closed to energize relay R3. The energization of relay R3 opens its normally closed contacts Ra to interrupt the circuit which energizes solenoid 1, thereby permitting the valve E84 to spring return to a position directing compressed air to the bottom of cylinders 122 and 124 and causing the piston rods 126 and 12S to be raised. It should be noted that if for any reason the suction cups i3d and 138 fail to hold the sheet and the sheet is dropped back down onto the pile, limit switch L84 will be opened to cause the suction cups to again descend onto the top of the pile and pick up the piece which has been dropped. When the suction cups and piston rods are fully retracted, the channel member 134 will engage limit switch L89 to cause its contacts to open. ln the meantime, contacts Rb will have been opened by the energization of relay R3 and contacts RSa and limit switch L82 remain in their normally open positions. Thus, the circuit energizing relay R2 is interrupted. The deenergization of relay R2 `causes the opening of contacts RfZa and thus the deenergization of solenoid 3. Deenergization of solenoid 3` permits the spool of valve 182 to spring return to a position in which compressed air is delivered to the cylinder 102 in a direction causing retracted downward movement of the piston rod ido. The rocker frame 7d is thus moved to its rearward position as illustrated in broken lines in FIG. 3. In so doing, it permits limit switch L87 to open and contacts limit switch L86 to close its contacts LSoa and LS6b. The opening of contacts 1.86ct terminates operation of the roller coater motor 17d, while the opening of contacts L86b deenergizes solenoid 2, which operates the vacuum control switch 14A and admits atmosphere to the vacuum cups 133 and 138, thereby releasing the sheet held by said vacuum cups and penrnitting it to drop onto the conveyor i6. As the workpiece drops onto the conveyor I6, it contacts limit switch L83-, the actuating arm or" which projects above the rows of rollers 38 and l0 to cause its contacts to close and thus energize relay R5. When relay R5 is energized, its contacts RSa and RSb close. A circuit is now completed through switch SW2 and contacts R5a to energize relay R2. This produces closure of contacts R2a and establishes an energizing circuit for solenoid 3 which shifts valve 182 to a position in which air is admitted to the cylinder M2 in a direction extending the piston rod llltiti and causing forward rocking movement o the rocker frame 70. As soon as the rocker frame 'itl begins its lforward movement and moves out of contact with the limit switch L86, the contacts LSda vll close to establish an energizing circuit for relay Rd through switch SW1, limit switch LST and the now closed contacts Rb. The energization of relay RI produces closure of the contacts Ria thereof to energize solenoid d which is operatively connected to a valve 188 which is connected to cylinder 68. The energization of solenoid 4 operates valve 13S to admit air to the cylinder 68 in a direction causing movement of the piston rod 66 in a left-hand direction, as viewed in FIG. 4. The dog Si? is thus moved into engagement with one end of the sheet resting on the conveyor ld and pushes the sheet into the roller coater. In the event that a particularly long sheet is being handled, one end thereof will have come to rest on the dog Litt, pivoting it downwardly. In this event, the dog S2 will engage the sheet and serve in place of the dog 5G. The rolls of the roller coater which were again driven in rotation upon the closure of limit switch contacts LSta, grasp the sheet and draw it through the roller coater. As the sheet moves out of engagement with limit switch L83, relay R5 is deenergized to cause its contacts RSb to open, thereby deenergizing the relay Rl, which causes its contacts Ria to open. This breaks the energizing circuit to solenoid d and permits the valve lS to spring return to a position in which compressed air is admitted to the cylinder 63 in a direction causing the piston rod 66 to move in a right-hand direction, as viewed in FIG. 4, thereby positioning the slide I8 out of alignment with the position on the conveyor I6 onto which sheets are dropped by the transfer mechanism I4.

The transfer cycle continues to operate in the cycle previously described except that the limit switch L88, being held lclosed by the presence of the stack in unloading position on the conveyor l2, keeps the relay R4 energized to prevent energization of the conveyor motor relay NIZ. In the event that a sheet has failed to clear the conveyor I6 by the time that the rocker frame has lifted a sheet olf of the stack and is ready to retract, the sheet which is on the conveyor lo will hold the limit switch L82 closed to establish an energizing circuit for relay R2, bypassing the limit switch L89, thereby maintaining 7 the contacts R25; closed and continuing the energization of solenoid 3' to prevent the rocker frame from moving a newV sheet over the conveyor 16. Limit switches LSll andLSS also serve a regulating function. In the event that both of these ylimit switches are held open by the presence of sheets on the conveyor 22, the circuits for relays Rt and Md will be interrupted and the solenoidv 4-A will be prevented from being energized, thereby preventing the movement of the dog Islide 18 and also preventingthe operation of the `roller coater motor 170. From the' foregoing, it will be seen Vthat the operation of the,V mechanism of the present invention isV such as to provide for the' automatic and successive depiling (of a stack of sheet material asrapidly as a receiving station is in a condition ready to receive the sheets. Furthermore,the conveyor 12 will be automatically operated to advance successive :stacks of sheetsinto a position in which they are adaptedto be depiledA by the transfer mechanism 14. Furthermore, it will be seen that theV shape and arrangement of the transfer `mech'anisin 14 is s uch as to occupy al minimum of floor space over and above that required by the conveyor. The frame member 70 is so supported that a minimum amount of energy is needed to rock the frame between its two positions. lThis largely results from the fact that the weight of the frame and the sheet carried thereby is very nearly balanced over the pivot axisof the rocker frame throughout the extent of the movement of Athe rocker frame` In addition, the sheet travels in a relatively fiat arc as the rocker frame is moved and thus thelevel of the 'sheet remains substantially unchanged from one position of the rocker frame to the other.' ltwill also be appreciated that the tubular framework of Ithe rocker frame provides a convenient and highly advantageous method fork connecting the vacuum pump tot-he suction cups. The suction cups, which are preferably made `from a flexible rubber material, are such, as' to tightly engage the sheets around the periphery thereof andrin practice it has been found that a pair of .vacuum cups is a'ble to lift an extremely heavy piece of sheet steel without difficulty.

'VA suitably high vacuum llevel is maintained within the rocker frame 7G by means of a pressure responsive switch 180 which isYV tapped into the cross frame; member 7d; TheV switch ,1861s provided with contacts 18651 which are normally'closed tov energize a motor starter relay M3, thereby maintaining its contacts M3a, M3b and M3C closed to deliver current to a vacuum pump motor 196 which operates the vacuum pump '74.' When the vacuum level within the rocker frame 7i) reaches a suitably high level, the contacts oa will be opened to deenergize relayMS and Ythus Adeenergize motor 199. Thus, the motor v190 is only operated when a need for a higher vacuum level exists. y j

While it will be apparent that the preferred embodiment herein illustrated isV well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

l. A transfer mechanism including two adjacent supporting surfaces, a transfer arm having a lower section extending upwardly under one of said supporting surfaces and beyond the outside edge thereof .and an upper section extending upwardiy and inwardly toward a midplane extending between said supporting surfaces so as to be alternatively positionable over one or the other of said supporting sur-faces, work enga-ging and supporting means on said upper section, and means for rocking said transfer arm to position said work engaging and supporting means selectively over said supporting sur-faces.

' Z. A transfer mechanism including two adjacent supporting surfaces, a transfer Iarm having a lower section extending upwardly under one of said supporting surfaces and lbeyond the outside edge thereof and an upper section 8 extending upwardly and inwardly toward a midplane extending between said supporting surfaces so as to be alternatively positionable over one or the other of said supporting surfaces, a lifting mechanism pivotally suspended from said upper section for enga-ging and lifting pieces of material, and means for rocking said transfer arm between a position in which said lifting mechanism is disposed over one of said supporting surfaces and a position in which said lifting mechanism is disposed over the other of said supporting surfaces.

'5. The .structure set forth lin'clarim 2 including means frxedly secured to said upper section engageable with said lifting mechanismv forl limitingrpivotal swinging movement thereof upon movement of said rocker frame between said positions. Y

A transfer mechanismY including two adjacent supporting surfaces, .a transfer arm havingra lower section extending upwardly under oneof said supporting surfaces and beyond the outside edge thereof and an upper section extending upwardly and inwardly toward la midplane extending between said supporting surfaces so as to be alternatively positionable over one or .the other ofsaid supporting surfaces, a lifting mechanismpivotally suspended from said uppernse'ctionforrengaging and lifting pieces of material, a pivotal support fordsaid transfer arm disosed beneath the level of said supporting surfaces, and a power cylinder having a piston rod connected to said lower section for rocking said tranfser arm between a position in which said lifting mechanism is disposed over one of said supporting surfaces and a position in which said lifting mechanism is disposed over the other of said supporting surfaces.

5. A transfer mechanism includingrtwo adjacent supporting surfaces, a transfer arm having a lower section extending upwardly underV one of said supporting surfaces and beyond the outside edge Ythereof and an upper section extending upwardly land inwardly/*toward a midplane extending Vbetween said supporting surfaces so as .to be alternatively positionable over orieor the other of said supporting surfaces, said transfer arm having hollow tubular frame elements defining portions of said upper and lower sections and providinga iluid chamber, a downwardly facing suction cup pivotally suspended from said upper section for vertical movement relative thereto, a vacuum pump connected to ysaid iluid chamber, and means connecting said fluid .chamber to said suction cup whereby air may be evacuated therefrom through said transfer arm.

v6. A transfer mechanism including two adjacent supporting surfaces, a transfer `arm having a lower sectionv extending upwardlyrunder one of said supporting surfaces and beyond the outside edge thereof and an upper section extending upwardly and inwardly toward a midplane extending between said supporting surfaces so as to be alternatively positionable over one or the other of said supporting sur-faces, a lifting mechanism pivotally suspended from said upper section and having a suction cup adapted to engage and lift a sheet of material on one of said supporting surfaces, a limit switch carried by said lifting mechanism actuated by a sheet of material in engagement with said suction cup, a control circuit for said .transfer ,arm including .said limit switch operable to cause said lifting mechanism to return to pick up a piece of material dropped by said suction cup prior to the normal full lifting cycle of said lifting mechanism, and means for rocking said rocker frame between a position in which said lifting mechanism is disposed over one of said supporting surfaces and a position in which said lifting mechanism is disposed over the other of said supporting surfaces.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A TRANSFER MECHANISM INCLUDING TWO ADJACENT SUPPORTING SURFACES, A TRANSFER ARM HAVING A LOWER SECTION EXTENDING UPWARDLY UNDER ONE OF SAID SUPPORTING SURFACES AND BEYOND THE OUTSIDE EDGE THEREOF AND AN UPPER SECTION EXTENDING UPWARDLY AND INWARDLY TOWARD A MIDPLANE EXTENDING BETWEEN SAID SUPPORTING SURFACES SO AS TO BE ALTERNATIVELY POSITIONABLE OVER ONE OR THE OTHER OF SAID SUPPORTING SURFACES, WORK ENGAGING AND SUPPORTING MEANS ON SAID UPPER SECTION, AND MEANS FOR ROCKING SAID TRANSFER ARM TO POSITION SAID WORK ENGAGING AND SUPPORTING MEANS SELECTIVELY OVER SAID SUPPORTING SURFACES. 